Hearing aids are wearable hearing apparatuses design to assist the hard of hearing. To meet the numerous individual needs, various designs of hearing aid such as behind-the-ear hearing aids (BTE), hearing aids with an external receiver (RIC: receiver in the canal) and in-the-ear hearing aids (ITE), e.g. including concha hearing aids or canal hearing aids (ITE, CIC), are provided. The hearing aids listed by way of example are worn on the outer ear or in the auditory canal. However, bone conduction hearing aids, implantable or vibrotactile hearing aids are also available on the market, in which the damaged hearing is stimulated either mechanically or electrically.
In principal the main components of a hearing aid are an input converter, an amplifier and an output converter. The input converter is generally a sound receiver, e.g. a microphone, and/or an electromagnetic receiver, e.g. an induction coil. The output converter is mostly implemented as an electroacoustic converter, e.g. miniature loudspeaker, or as an electromagnetic converter, e.g. bone conduction receiver. The amplifier is normally integrated into a signal processing unit. This basic structure is illustrated in FIG. 1 using the example of a behind-the-ear hearing aid. A hearing aid housing 1 for wearing behind the ear incorporates one or more microphones 2 to receive the sound from the environment. A signal processing unit 3, likewise integrated into the hearing aid housing 1, processes the microphone signals and amplifies them. The output signal from the signal processing unit 3 is transferred to a loudspeaker or receiver 4 which emits an acoustic signal. The sound is if necessary transferred to the ear drum of the hearing aid wearer via a sound tube which is fixed in the auditory canal with an otoplastic. The hearing aid and in particular the signal processing unit 3 is supplied with power by a battery 5 likewise integrated into the hearing aid housing 1.